This application relates to the art of heat exchangers and, more particularly, to heat exchangers of the type wherein a material is conveyed along a housing in contact with a rotary heat exchanger through which a heat exchange medium passes. The invention is particularly applicable to rotary conveying screw heat exchangers, and will be described with specific reference thereto. However, it will be appreciated that the invention has broader aspects, and certain features may be used in other environments, such as in conveying screws used for conveying materials without exchanging heat.
Rotary conveying screw exchangers are rotatably supported at their opposite end portions, and the central portion of the conveying screw is highly stressed as material is forced to move therealong. Welding a helical flight along the cylindrical body of the conveying screw is very expensive because it is time consuming. In addition, welding along the central portion of the conveying screw body causes stress risers, which are sources of fatigue failure. It would be desirable to have an arrangement for attaching a helical flight to a cylindrical body of a conveying screw without welding along the central portion of the conveying screw body.